I had a problem with the washer fluid light coming on all the time. I would try to add more fluid and it would only take a drop or two. I eventually replaced the sensor, but the problem returned. After tearing into the system I discovered that there is a filter in the neck of the tank, it looks like a condom hanging down in there. This was causing the fluid to back up when I poured it in, acting like it was full, when the tank was still low. Either remove the filter, it pulls straight up out of the tank, or try pouring the fluid in very slowly. I felt rather stupid when I finally figured this out!